Method of polishing a silicon-containing dielectric

ABSTRACT

The invention is directed to a method of polishing a silicon-containing dielectric layer involving the use of a chemical-mechanical polishing system comprising (a) an inorganic abrasive, (b) a polishing additive, and (c) a liquid carrier, wherein the polishing composition has a pH of about 4 to about 6. The polishing additive comprises a functional group having a pK a  of about 4 to about 9 and is selected from the group consisting of arylamines, aminoalcohols, aliphatic amines, heterocyclic amines, hydroxamic acids, aminocarboxylic acids, cyclic monocarboxylic acids, unsaturated monocarboxylic acids, substituted phenols, sulfonamides, thiols, salts thereof, and combinations thereof. The invention is further directed to the chemical-mechanical polishing system, wherein the inorganic abrasive is ceria.

FIELD OF THE INVENTION

This invention pertains to a method of polishing a silicon-containingdielectric substrate.

BACKGROUND OF THE INVENTION

Compositions and methods for planarizing or polishing the surface of asubstrate are well known in the art. Polishing compositions (also knownas polishing slurries) typically contain an abrasive material in anaqueous solution and are applied to a surface by contacting the surfacewith a polishing pad saturated with the polishing composition. Typicalabrasive materials include silicon dioxide, cerium oxide, aluminumoxide, zirconium oxide, and tin oxide. U.S. Pat. No. 5,527,423, forexample, describes a method for chemically-mechanically polishing ametal layer by contacting the surface with a polishing slurry comprisinghigh purity fine metal oxide particles in an aqueous medium. Thepolishing slurry is typically used in conjunction with a polishing pad(e.g., polishing cloth or disk). Suitable polishing pads are describedin U.S. Pat. Nos. 6,062,968, 6,117,000, and 6,126,532, which disclosethe use of sintered polyurethane polishing pads having an open-celledporous network, and U.S. Pat. No. 5,489,233, which discloses the use ofsolid polishing pads having a surface texture or pattern. Alternatively,the abrasive material may be incorporated into the polishing pad. U.S.Pat. No. 5,958,794 discloses a fixed abrasive polishing pad.

Conventional polishing systems and polishing methods typically are notentirely satisfactory at planarizing semiconductor wafers. Inparticular, polishing compositions and polishing pads can have less thandesirable polishing rates or polishing selectivities, and their use inchemically-mechanically polishing semiconductor surfaces can result inpoor surface quality. Because the performance of a semiconductor waferis directly associated with the planarity of its surface, it is crucialto use a polishing composition and method that results in a highpolishing efficiency, selectivity, uniformity, and removal rate andleaves a high quality polish with minimal surface defects.

The difficulty in creating an effective polishing system forsemiconductor wafers stems from the complexity of the semiconductorwafer. Semiconductor wafers are typically composed of a substrate, onwhich a plurality of transistors has been formed. Integrated circuitsare chemically and physically connected into a substrate by patterningregions in the substrate and layers on the substrate. To produce anoperable semiconductor wafer and to maximize the yield, performance, andreliability of the wafer, it is desirable to polish select surfaces ofthe wafer without adversely affecting underlying structures ortopography. In fact, various problems in semiconductor fabrication canoccur if the process steps are not performed on wafer surfaces that areadequately planarized.

Typically, polishing compositions for polishing dielectric materialsrequire an alkaline pH in order to obtain sufficient removal rates forthe dielectric. For example, U.S. Pat. Nos. 4,169,337, 4,462,188, and4,867,757 disclose polishing compositions for silicon dioxide removalcomprising silica abrasives at an alkaline pH. Similarly, WO 00/25984,WO 01/56070, and WO 02/01620 disclose polishing compositions for ShallowTrench Isolation (STI) polishing comprising fumed silica at alkaline pH.EP 853 110 A1 describes a polishing composition having a pH of 11–13,which purportedly increase selectivity in STI polishing. U.S. PatentApplication Publication 2001/0051433 A1 discloses a polishingcomposition for dielectric chemical-mechanical polishing (CMP)comprising filmed silica and a cesium salt with a pH of 7 or greater.Such alkaline polishing compositions, while effective in the removal ofsilicon dioxide dielectric materials, provide poor selectivity insubstrates comprising both silicon dioxide and silicon nitride layers,as in STI substrates. The use of chelating acid additives to improve theselectivity in STI polishing is known in the art. For example, U.S. Pat.Nos. 5,738,800, 6,042,741, 6,132,637, and 6,218,305 disclose the use ofacid-containing complexing agents in polishing compositions comprisingan abrasive (e.g., ceria or silica). U.S. Pat. No. 5,614,444 disclosesthe use of chemical additives comprising anionic, cationic, or nonionicpolar groups and apolar organic components to suppress the removal of adielectric material. EP 1 061 111 A1 discloses polishing compositionsfor STI polishing comprising ceria abrasive and an organic compoundcomprising a carboxylic acid or sulfonic acid group.

A need remains, however, for polishing systems and polishing methodsthat will exhibit desirable planarization efficiency, selectivity,uniformity, and removal rate during the polishing and planarization ofdielectric substrates, while minimizing defectivity, such as surfaceimperfections and damage to underlying structures and topography duringpolishing and planarization. The invention seeks to provide such achemical-mechanical polishing system and method. These and otheradvantages of the invention will be apparent from the description of theinvention provided herein.

BRIEF SUMMARY OF THE INVENTION

The invention provides a method of polishing a substrate comprising (i)contacting a substrate comprising a silicon-containing dielectric layerwith a chemical-mechanical polishing system and (ii) abrading at least aportion of the silicon-containing dielectric layer to polish thesubstrate. The chemical-mechanical polishing system comprises (a) aninorganic abrasive, (b) a polishing additive bearing a functional groupwith a pK_(a) of about 4 to about 9, and (c) a liquid carrier. Thepolishing additive is a compound selected from the group consisting ofarylamines, aminoalcohols, aliphatic amines, heterocyclic amines,hydroxamic acids, aminocarboxylic acids, cyclic monocarboxylic acids,unsaturated monocarboxylic acids, substituted phenols, sulfonamides,thiols, salts thereof, and combinations thereof. The polishingcomposition has a pH of about 7 or less and does not contain asignificant amount of cross-linked polymer abrasive particles that areelectrostatically associated with the inorganic abrasive particles. Thefunctional group desirably is selected from amines, carboxylic acids,alcohols, thiols, sulfonamides, imides, hydroxamic acids, barbituricacids, salts thereof, and combinations thereof.

The invention further provides a chemical-mechanical polishingcomposition comprising (a) ceria abrasive having an average particlesize of about 150 nm or less, (b) a polishing additive bearing afunctional group with a pK_(a) of about 4 to about 9, wherein thepolishing additive is a compound selected from the group consisting ofarylamines, aminoalcohols, aliphatic amines, heterocyclic amines,hydroxamic acids, aminocarboxylic acids, cyclic monocarboxylic acids,unsaturated monocarboxylic acids, substituted phenols, sulfonamides,thiols, salts thereof, and combinations thereof, and (c) a liquidcarrier. The chemical-mechanical polishing composition has a pH of about3 to about 6.

DETAILED DESCRIPTION OF THE INVENTION

The invention is directed to a chemical-mechanical polishing (CMP)system comprising (a) an abrasive, (b) a polishing additive bearing afunctional group with a pK_(a) of about 4 to about 9, and (c) a liquidcarrier, and a method of polishing a substrate comprising asilicon-containing dielectric layer using the CMP system.

The CMP system described herein comprises an inorganic abrasive. Theinorganic abrasive can be in any suitable form (e.g., abrasiveparticles) and can be suspended in the liquid carrier or can be fixedonto a polishing surface of a polishing pad. The polishing pad can beany suitable polishing pad. The polishing additive and any othercomponents suspended in the liquid carrier (e.g., the abrasive) form apolishing composition of the CMP system.

In a first embodiment, the inorganic abrasive can be any suitableinorganic abrasive. For example, the inorganic abrasive can be a metaloxide abrasive selected from the group consisting of alumina (e.g.,α-alumina, γ-alumina, δ-alumina, and fumed alumina), silica (e.g.,colloidally dispersed condensation-polymerized silica, precipitatedsilica, and fumed silica), ceria, titania, zirconia, chromia, ironoxide, germania, magnesia, co-formed products thereof, and combinationsthereof. The inorganic abrasive also can be silicon carbide, boronnitride, and the like. The metal oxide abrasive optionally can beelectrostatically coated with an oppositely-charged polyelectrolyte, forexample, polyelectrolyte-coated alumina abrasive such aspolystyrenesulfonic acid-coated alumina. The CMP system does not containany significant amount of cross-linked polymer abrasive particles thatare electrostatically associated with the inorganic-abrasive particles.The introduction of cross-linked polymer abrasives can reduce theoverall polishing removal rates. Thus, the amount of cross-linkedpolymer abrasive particles present in the CMP system should besufficiently low so as not to interfere with the polishing properties ofthe inorganic abrasive. Preferably, the CMP system contains an amount ofcross-linked polymer particles that is less than about 10% by weight(e.g., less than about 5% by weight or less than about 1% by weight) ofthe amount of inorganic particles. The CMP system preferably does notcontain any cross-linked polymer abrasive particles that areelectrostatically associated with the inorganic abrasive particles.

Preferably, the inorganic abrasive is a cationic abrasive, morepreferably ceria. The ceria can be produced by any suitable method. Onetype of ceria abrasive commonly used in semiconductor polishing, inparticular shallow trench isolation processing, is ceria produced by avapor phase synthesis such as described in U.S. Pat. Nos. 5,460,701,5,514,349, and 5,874,684. Such ceria abrasives are sold by NanophaseTechnologies, for example, as NanoTek® cerium oxide, and FerroCorporation. Other suitable ceria abrasives include precipitated ceriaabrasives formed by hydrothermal processes, such as those sold byAdvanced Nano Products and Rhodia.

The inorganic abrasive can have any suitable primary particle size.Typically, the abrasive has an average primary particle size of about200 nm or less (e.g, about 180 nm or less). Preferably, the inorganicabrasive has an average primary particle size of about 160 nm or less(e.g., about 140 nm or less). The primary particle size desirably ismeasured by a laser diffraction technique. The CMP compositionpreferably is resistant to particle agglomeration such that the averageagglomerate particle size is about 300 nm or less (e.g., 250 nm or less,or even 200 nm or less). The absence of agglomeration is also reflectedin the overall width of the particle size distribution, which typicallyis ± about 35% (e.g., ± about 25%, or even ± about 15%) of the averageprimary particle size.

In a second embodiment, the inorganic abrasive comprises (consists of orconsists essentially of) ceria. Preferably, the ceria abrasive does notcontain any significant amount of cross-linked polymer abrasiveparticles that are electrostatically associated with the ceria. Morepreferably, the ceria abrasive does not contain any cross-linked polymerabrasive particles that are electrostatically associated with the ceria.The ceria abrasive preferably has an average primary particle size ofabout 180 nm or less, more preferably about 150 nm or less (or evenabout 140 nm or less). Typically, the ceria abrasive has an averageparticle size of about 20 nm or more (e.g., about 50 nm or more). Theoverall width of the particle size distribution preferably is ± about50% (e.g., ± about 40%, ± about 30%, or even ± about 20%) of the averageprimary particle size. For some applications, it is preferred that theceria be suspended in the liquid carrier. In other applications, it ispreferred that the ceria be fixed onto a polishing surface of apolishing pad.

The inorganic abrasive of either the first or second embodiment, whensuspended in the liquid carrier, preferably is colloidally stable. Theterm colloid refers to the suspension of abrasive particles in theliquid carrier. Colloidal stability refers to the maintenance of thatsuspension through time. In the context of this invention, an abrasiveis considered colloidally stable if, when the abrasive is placed into a100 ml graduated cylinder and allowed to stand unagitated for a time of2 hours, the difference between the concentration of particles in thebottom 50 ml of the graduated cylinder ([B] in terms of g/ml) and theconcentration of particles in the top 50 ml of the graduated cylinder([T] in terms of g/ml) divided by the initial concentration of particlesin the abrasive composition ([C] in terms of g/ml) is less than or equalto 0.5 (i.e., {[B]−[T]}/[C]≦0.5). More preferably, the value of[B]−[T]/[C] desirably is less than or equal to 0.3, and preferably isless than or equal to 0.1.

The inorganic abrasive according to either the first or secondembodiment typically has a positive zeta potential at the pH of thepolishing composition. Preferably, the positive zeta potential of theinorganic abrasive is maintained upon combination with the polishingadditive in the polishing composition. The zeta potential of an abrasiverefers to the difference between the electrical charge of the ionssurrounding the abrasive and the electrical charge of the bulk solution(e.g., the liquid carrier and any other components dissolved therein).The zeta potential of the inorganic abrasive will vary with pH. The zetapotential of ceria at pH of 5 in 40 mM KCl is about +32 mV. Desirably,the polishing additive does not interact strongly with the abrasive soas to cause reversal of the zeta potential, which can lead toagglomeration of the abrasive particles and settling. Preferably, thepolishing composition has a low conductivity (e.g., ionic strength), forexample a conductivity value of less than about 2000 μS/cm (e.g., lessthan about 1500 μS/cm) at a pH of about 5 and a conductivity value ofless than about 500 μS/cm at a pH of about 4. A low conductivity valuereflects that only a small amount of base is required to adjust the pHto the desired range.

When the abrasive is suspended in the liquid carrier, the polishingcomposition typically comprises about 0.01 wt. % to about 10 wt. %(e.g., about 0.02 wt. % to about 5 wt. %, or about 0.05 wt. % to about 1wt. %) inorganic abrasive, based on the weight of the liquid carrier andany components dissolved or suspended therein. Preferably, the polishingcomposition comprises about 0.1 wt. % to about 0.5 wt. % inorganicabrasive.

The polishing additive is included in the polishing composition tomodify the surface properties of the silicon-containing dielectric layerbeing polished so as to make the surface more receptive to interactionwith abrasive particles. The pH of the polishing composition plays animportant role in determining the interactions between the polishingadditives and the surface of the silicon-containing dielectric layer.The polishing composition typically has a pH of about 7 or less,preferably about 2 to about 6.5, more preferably about 3 to about 6(e.g., about 3.5 to about 5.5). In order for the polishing additive tointeract with the silicon-containing dielectric layers within this pHrange, the polishing additive desirably bears a functional group havinga pK_(a) (in water) of about 4 to about 9, preferably about 4 to about 7(e.g., about 4 to about 6). Moreover, it is desirable that the polishingadditive has an overall net charge that is more positive than about −1(e.g., a net charge=0, +1, +2, etc.). The net charge is determined to bethe charge of the polishing additive when the functional group having apK_(a) in the range of about 4 to about 9 is protonated.

The functional group of the polishing additive can be any suitablefunctional group, and typically is selected from amines, carboxylicacids, alcohols, thiols, sulfonamides, imides, hydroxamic acids,barbituric acids, hydrazines, amidoxines, salts thereof, andcombinations thereof. Polishing additives bearing these functionalgroups and having a pK_(a) in the range of about 4 to about 9 includecompounds selected from the group consisting of arylamines,aminoalcohols, aliphatic amines, heterocyclic amines, hydroxamic acids,aminocarboxylic acids, cyclic monocarboxylic acids, unsaturatedmonocarboxylic acids, substituted phenols, sulfonamides, thiols, andcombinations thereof. Preferably, the polishing additive is selectedfrom the group consisting of arylamines, heterocyclic amines,aminocarboxylic acids, and combinations thereof. Any of the foregoingpolishing additives may exist in the form of a salt, for example a saltselected from the group consisting of hydrochloride salts, hydrobromidesalts, sulfate salts, sulfonate salts, trifluoromethanesulfonate salts,acetate salts, trifluoroacetate salts, picrate salts, perfluorobutyratesalts, sodium salts, potassium salts, ammonium salts, halide salts, orthe like.

The arylamine can be any suitable arylamine having a pK_(a) of about 4to about 9. Preferably, the arylamine is a primary arylamine. Thearylamine optionally can be substituted with one or more substituentsselected from the group consisting of C₁₋₁₂ alkyl, C₁₋₁₂ alkoxy, C₆₋₁₂aryl, carboxylic acid, sulfonic acid, phosphonic acid, hydroxyl, thiol,sulfonamide, acetamide, salts thereof, and combinations thereof. Forexample, the arylamine can be aniline, 4-chloroaniline,3-methoxyaniline, N-methylaniline, 4-methoxyaniline, p-toluidine,anthranilic acid, 3-amino-4-hydroxybenzene sulfonic acid,aminobenzylalcohol, aminobenzylamine, 1-(2-aminophenyl)pyrrole,1-(3-aminophenyl)ethanol, 2-aminophenylether,2,5-bis-(4-aminophenyl)-1,3,4-oxadiazole,2-(2-aminophenyl)-1H-1,3,4-triazole, 2-aminophenol, 3-aminophenol,4-aminophenol, dimethylaminophenol, 2-aminothiolphenol,3-aminothiolphenol, 4-aminothiolphenol, 4-aminophenyl methyl sulfide,2-aminobenzenesulfonamide, orthanilic acid, 3-aminobenzene boronic acid,5-aminoisophthalic acid, sulfacetamide, sulfanilic acid, o- orp-arsanilic acid, (3R)-3-(4-trifluoromethylphenylamino)pentanoic acidamide, salts thereof, and combinations thereof.

The aminoalcohol can be any suitable aminoalcohol having a pK_(a) ofabout 4 to about 9. For example aminoalcohols can be selected from thegroup consisting of triethanolamine, benzyldiethanolamine,tris(hydroxymethyl)aminomethane, hydroxylamine, tetracycline, saltsthereof, and combinations thereof. Preferably, the aminoalcohol is atertiary aminoalcohol.

The aliphatic amine can be any suitable aliphatic amine having a pK_(a)of about 4 to about 9. Preferably, the aliphatic amine is selected fromthe group consisting of methoxyamine, hydroxylamine,N-methylhydroxylamine, N,O-dimethylhydroxylamine, β-difluoroethylamine,ethylenediamine, triethylenediamine,diethyl((butylamino)(2-hydroxyphenyl) methyl)phosphonate, iminoethanes,iminobutanes, triallylamine, cyanoamines (e.g., aminoacetonitrile,diethylaminoacetonitrile, 2-amino-2-cyanopropane,isopropylaminopropionitrile, diethylaminopropionitrile,aminopropionitrile, dicyanodiethylamine),3-(dimethylamino)propionitrile), salts thereof, and combinationsthereof. The aliphatic amine can also be a hydrazine. Preferably, thehydrazine is selected from the group consisting of hydrazine,methylhydrazine, tetramethylhydrazine, N,N-diethylhydrazine,phenylhydrazine, N,N-dimethylhydrazine, trimethylhydrazine,ethylhydrazine, salts thereof (e.g., hydrochloride salts), andcombinations thereof.

The heterocyclic amine can be any suitable heterocyclic amine having apK_(a) of about 4 to about 9, including monocyclic, bicyclic, andtricyclic amines. Typically, the cyclic amine is a 3-, 4-, 5- or6-membered cyclic structure comprising one or more nitrogen atoms.Preferably, the cyclic amine is a 5- or 6-membered cyclic structure. Theheterocyclic amine optionally is substituted by one or more substituentsselected from the group consisting of H, OH, COOH, SO₃H, PO₃H, Br, Cl,I, F, NO₂, hydrazine, a C₁₋₈ alkyl (optionally substituted with OH,COOH, Br, Cl, I, or NO₂), a C₆₋₁₂ aryl (optionally substituted with OH,COOH, Br, I, or NO₂), C(O)H, C(O)R (where R is a C₁₋₈ alkyl or a C₆₋₁₂aryl), and a C₁₋₈ alkenyl. Desirably, the heterocyclic amine contains atleast one unsubstituted heterocyclic nitrogen. For example, theheterocyclic amine can be imidazole, 1-methylimidazole,2-methylimidazole, 2-ethylimidazole, 2-hydroxymethylimidazole,1-methyl-2-hydroxymethylimidazole, benzimidazole, quinoline,isoquinoline, hydroxyquinoline, melamine, pyridine, bipyridine,2-methylpyridine, 4-methylpyridine, 2-aminopyridine, 3-aminopyridine,2,3-pyridinedicarboxylic acid, 2,5-pyridinedicarboxylic acid,2,6-pyridinedicarboxylic acid, 5-butyl-2-pyridinecarboxylic acid,4-hydroxy-2-pyridinecarboxylic acid, 3-hydroxy-2-pyridinecarboxylicacid, 2-pyridinecarboxylic acid, 3-benzoyl-2-pyridinecarboxylic acid,6-methyl-2-pyridinecarboxylic acid, 3-methyl-2-pyridinecarboxylic acid,6-bromo-2-pyridinecarboxylic acid, 6-chloro-2-pyridinecarboxylic acid,3,6-dichloro-2-pyridinecarboxylic acid,4-hydrazino-3,5,6-trichloro-2-pyridinecarboxylic acid, quinoline,isoquinoline, 2-quinolinecarboxylic acid,4-methoxy-2-quinolinecarboxylic acid, 8-hydroxy-2-quinolinecarboxylicacid, 4,8-dihydroxy-2-quinolinecarboxylic acid,7-chloro-4-hydroxy-2-quinolinecarboxylic acid,5,7-dichloro-4-hydroxy-2-quinolinecarboxylic acid,5-nitro-2-quinolinecarboxylic acid, 1-isoquinolinecarboxylic acid,3-isoquinolinecarboxylic acid, acridine, benzoquinoline, benzacridine,clonidine, anabasine, nornicotine, triazolopyridine, pyridoxine,serotonin, histamine, benzodiazepine, aziridine, morpholine, 1,8diazabicyclo(5,4,0)undecene-7 (DABCO), hexamethylenetetramine,piperazine, N-benzoylpiperazine, 1-tosylpiperazine,N-carbethoxypiperazine, 1,2,3-triazole, 1,2,4-triazole, 2-aminothiazole,pyrrole, pyrrole-2-carboxylic acid and alkyl, halo, or carboxylicacid-substituted derivatives thereof, 3-pyrroline-2-carboxylic acid,ethylpyrroline, benzylpyrroline, cyclohexylpyrroline, tolylpyrroline,tetrazole, 5-cyclopropyltetrazole, 5-methyltetrazole,5-hydroxytetrazole, 5-phenoxytetrazole, 5-phenyltetrazole, saltsthereof, and combinations thereof. The heterocylic amine also can be animide, an aminidine, or a barbituric acid compound. For example,suitable imides include those selected from the group consisting offluorouracil, methylthiouracil, 5,5-diphenylhydantoin,5,5-dimethyl-2,4-oxazolidinedione, phthalimide, succinimide,3,3-methylphenylglutarimide, 3,3-dimethylsuccinimide, salts thereof, andcombinations thereof. Suitable aminidines include those selected fromthe group consisting of imidazo[2,3-b]thioxazole,hydroxyimidazo[2,3-a]isoindole, salts thereof, and combinations thereof.Suitable barbituric acids include those selected from the groupconsisting of 5,5-methylphenylbarbituric acid, 1,5,5-trimethylbarbituricacid, hexobarbital, 5,5-dimethylbarbituric acid,1,5-dimethyl-5-phenylbarbituric acid, salts thereof, and combinationsthereof.

The hydroxamic acid can be any suitable hydroxamic acid having a pK_(a)of about 4 to about 9. Preferably, the hydroxamic acid is selected fromthe group consisting of formohydroxamic acid, acetohydroxamic acid,benzohydroxamic acid, salicylhydroxamic acid, 2-aminobenzohydroxamicacids, 2-chlorobenzohydroxamic acid, 2-fluorobenzohydroxamic acid,2-nitrobenzohydroxamic acid, 3-nitrobenzohydroxamic acid,4-aminobenzohydroxamic acid, 4-chlorobenzohydroxamic acid,4-fluorobenzohydroxamic acid, 4-nitrobenzohydroxamic acid,4-hydroxybenzohydroxamic acid, salts thereof, and combinations thereof.

The aminocarboxylic acid can be any suitable aminocarboxylic acid havinga pK_(a) of about 4 to about 9. Traditional aminocarboxylic acidcompounds such as proline, glycine, phenylglycine, and the like have apK_(a) of about 2–2.5 for the carboxylic acid moiety and about 9–10 forthe amino moiety and are not suitable for use in the context of theinvention. Contrastingly, aminocarboxylic acids selected from the groupconsisting of glutamic acid, beta-hydroxyglutamic acid, aspartic acid,asparagine, azaserine, cysteine, histidine, 3-methylhistidine, cytosine,7-aminocephalosporanic acid, and carnosine each contain a functionalgroup having a pK_(a) of in the range of about 4 to about 9.

The cyclic monocarboxylic acid can be any suitable cyclic monocarboxylicacid having a pK_(a) of about 4 to about 9. Di- and poly-carboxylicacids previously suggested for use in polishing silicon-containingdielectric layers can have a pK_(a) in the desired range, but have atotal charge that leads to undesirable agglomeration, adhesion, and/orrapid settling of the inorganic abrasive particles. Desirably, thecyclic carboxylic acid compound comprises a C₄₋₁₂ cyclic alkyl or C₆₋₁₂aryl group. The cyclic carboxylic acid compound optionally issubstituted by one or more substituents selected from H, OH, COOH, Br,Cl, I, F, NO₂, hydrazine, a C₁₋₈ alkyl (optionally substituted with OH,COOH, Br, Cl, I, or NO₂), a C₆₋₁₂ aryl (optionally substituted with OH,COOH, Br, I, or NO₂), C(O)H, C(O)R (where R is a C₁₋₈ alkyl or a C₆₋₁₂aryl), and C₁₋₈ alkenyl. Preferably, the cyclic carboxylic acid compoundis not a di- or poly-hydroxybenzoic acid. Suitable cyclic monocarboxylicacid compounds include those selected from the group consisting ofbenzoic acid, C₁₋₁₂-alkyl-substituted benzoic acids,C₁₋₁₂-alkoxy-substituted benzoic acids, naphthalene 2-carboxylic acid,cyclohexane carboxylic acid, cyclohexyl acetic acid, 2-phenylaceticacid, 4-hydroxybenzoic acid, 3-hydroxybenzoic acid,2-piperidinecarboxylic acid, cyclopropanecarboxylic acids (e.g., cis-and trans-2-methylcyclopropanecarboxylic acid), salts thereof, andcombinations thereof. Especially preferred polishing additives are4-hydroxybenzoic acid, cyclohexane carboxylic acid, benzoic acid, saltsthereof, and combinations thereof.

The unsaturated monocarboxylic acid can be any suitable unsaturatedmonocarboxylic acid (e.g., alkenecarboxylic acid) having a pK_(a) ofabout 4 to about 9. Typically, the unsaturated monocarboxylic acid is aC₃₋₆-alk-2-enoic acid. Preferably, the unsaturated monocarboxylic acidis selected from the group consisting of cinnamic acids, propenoic acids(e.g., acrylic acid, 3-chloroprop-2-enecarboxylic acid), butenoic acids(e.g., crotonic acid, 3-chlorobut-2-enecarboxylic acid,4-chlorobut-2-enecarboxylic acid), pentenoic acids (e.g., cis- ortrans-2-pentenoic acid, 2-methyl-2-pentenoic acid), hexenoic acids(e.g., 2-hexenoic acid, 3-ethyl-2-hexenoic acid), salts thereof, andcombinations thereof.

The substituted phenol can be any suitable substituted phenol having apK_(a) of about 4 to about 9. Preferably, the substituted phenolcontains a substituent selected from nitro, chloro, bromo, fluoro,cyano, alkoxycarbonyl, alkanoyl, acyl, alkylsulfonyl, and combinationsthereof. Suitable nitrophenols include those selected from the groupconsisting of nitrophenol, 2,6-dihalo-4-nitrophenols,2,6-di-C₁₋₁₂-alkyl-4-nitrophenols, 2,4-dinitrophenol 2,6-dinitrophenol,3,4-dinitrophenol, 2-C₁₋₁₂-alkyl-4,6-dinitrophenols,2-halo-4,6-dinitrophenols, dinitro-o-cresol, trinitrophenols such aspicric acid, salts thereof, and combinations thereof.

The sulfonamide can be any suitable sulfonamide having a pK_(a) of about4 to about 9. Preferably, the sulfonamide is selected from the groupconsisting of N-chlorotolylsulfonamide, dichlorophenamide, mafenide,nimesulide, sulfamethizole, sulfaperin, sulfacetamide, sulfadiazine,sulfadimethoxine, sulfamethazine, sulfapyridine, sulfaquinoxaline, saltsthereof, and combinations thereof.

The thiol can be any suitable thiol having a pK_(a) of about 4 to about9. Preferably, the thiol is selected from the group consisting ofhydrogen disulfide, cysteamine, cysteinylcysteine, methyl cysteine,thiophenol, p-Cl-thiophenol, o-aminothiophenol, o-mercaptophenylaceticacid, p-nitrobenzenethiol, 2-mercaptoethanesulfonate,N-dimethylcysteamine, dipropylcysteamine, diethylcysteamine,mercaptoethylmorpholine, methylthioglycolate, mercaptoethylamine,N-trimethylcysteine, glutathione, mercaptoethylepiperidine,diethylaminopropanethiol, salts thereof, and combinations thereof.

When the polishing additive is an arylamine, the polishing additivepreferably is selected from the group consisting of aniline, anthranilicacid, aminophenols, orthanilic acid, salts thereof, and combinationsthereof. When the polishing additive is a heterocyclic amine compound,the polishing additive preferably is selected from the group consistingof imidazole, quinoline, pyridine, 2-methylpyridine,2-pyridinecarboxylic acid, pyridinedicarboxylic acids,2-quinolinecarboxylic acid, morpholine, piperazine, triazoles, pyrrole,pyrrole-2-carboxylic acid, tetrazoles, salts thereof, and combinationsthereof. When the polishing additive is an aminocarboxylic acidcompound, the polishing additive preferably is selected from the groupconsisting of glutamic acid, aspartic acid, cysteine, histidine, saltsthereof, and combinations thereof. When the polishing additive is acyclic mono-carboxylic acid compound, the polishing additive preferablyis selected from the group consisting of benzoic acid, cyclohexanecarboxylic acid, cyclohexylacetic acid, 2-phenylacetic acid, saltsthereof, and combinations thereof.

The polishing composition typically comprises about 5 wt. % or less(e.g., about 2 wt. % or less) polishing additive. The polishingcomposition desirably comprises about 0.005 wt. % or more (e.g., about0.01 wt. % or more) polishing additive. Preferably, the polishingcomposition comprises about 1 wt. % or less (e.g., about 0.5 wt. % orless) polishing additive.

A liquid carrier is used to facilitate the application of the abrasive,the polishing additive, and any other components dissolved or suspendedtherein to the surface of a suitable substrate to be polished (e.g.,planarized). The liquid carrier is typically an aqueous carrier and canbe water alone, can comprise water and a suitable water-misciblesolvent, or can be an emulsion. Suitable water-miscible solvents includealcohols such as methanol, ethanol, and the like. In some embodiments,the liquid carrier comprises a supercritical fluid. Preferably, theaqueous carrier consists of water, more preferably deionized water. Theliquid carrier optionally further comprises solvents or surfactants toaid in the solubilization of the polishing additive to enhance theamount of the polishing additive at the substrate surface.

The polishing composition optionally further comprises one or morecomponents such as pH adjusters, regulators, or buffers, and the like,which further aid in the maintaining of the pH of the polishingcomposition within the desired range. Suitable pH adjusters, regulators,or buffers can include, for example, sodium hydroxide, potassiumhydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate,sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citricacid, potassium phosphate, mixtures thereof, and the like.

The polishing composition optionally further comprises other components,such as biocides, anti-foaming agents, and the like. The biocide can beany suitable biocide, for example an isothiazolinone biocide. The amountof biocide used in the polishing composition typically is about 1 toabout 50 ppm, preferably about 10 to about 20 ppm based on the liquidcarrier and any components dissolved or suspended therein. Theanti-foaming agent can be any suitable anti-foaming agent. For example,the anti-foaming agent can be a polydimethylsiloxane polymer. The amountof anti-foaming agent present in the polishing composition typically isabout 40 to about 140 ppm based on the liquid carrier and any componentsdissolved or suspended therein.

The polishing composition optionally further comprises an alcohol.Preferably, the alcohol is methanol, ethanol, or propanol. Morepreferably, the alcohol is methanol. Typically, the alcohol is presentin the polishing composition in an amount of about 0.01 wt. % or morebased on the liquid carrier and any components dissolved or suspendedtherein. The alcohol also typically is present in the polishingcomposition in an amount of about 2 wt. % or less based on the liquidcarrier and any components dissolved or suspended therein.

The polishing composition optionally further comprises a surfactant toimprove polishing selectivity and/or planarity. The surfactant can beany suitable surfactant and can be a cationic surfactant, anionicsurfactant (e.g., polyacrylates), zwitterionic surfactant, nonionicsurfactant, or combination thereof. Preferably, the surfactant is azwitterionic surfactant or a nonionic surfactant. Suitable zwitterionicsurfactants include ammonium carboxylates, ammonium sulfates, amineoxides, N-dodecyl-N,N-dimethylbetaine, betaine, sulfobetaine,alkylammoniopropyl sulfate, and the like. Suitable nonionic surfactantsinclude acetylenic glycol surfactants such as2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate surfactants,polyoxyethylene C₆₋₃₀ alkyl ethers, polyoxyethylene C₆₋₃₀ alkyl acidesters, polyoxyethylene C₆₋₃₀ alkylphenyl ethers, polyoxyethylene C₆₋₃₀alkylcyclohexyl ethers, sorbitan C₆₋₃₀ alkyl acid esters,polyoxyethylenesorbitan C₆₋₃₀ alkyl acid esters, ethylenediaminepolyoxyethylenes, and the like. The amount of surfactant typically isabout 0.01 wt. % to about 5 wt. % based on the liquid carrier and anycomponents dissolved or suspended therein.

The CMP system is intended for use in polishing (e.g., planarizing) asilicon-containing dielectric layer of a substrate. The method ofpolishing a substrate comprises (i) providing the CMP system, (ii)contacting the substrate with the CMP system, and (iii) abrading atleast a portion of the substrate to polish the substrate. Preferably,the dielectric layer comprises (i.e., makes up) about 95% or more (e.g.,about 97% or more, or even about 99% or more) of the total surface areaof the substrate. The substrate can be any suitable substrate (e.g., anintegrated circuit, interlayer dielectric device (ILD), pre-metaldielectric substrate, glass substrate, optic, rigid disk, semiconductor,micro-electro-mechanical system, and low and high dielectric constantfilm) and can contain any suitable dielectric layer (e.g., insulatinglayer). The substrate typically is a microelectronic (e.g.,semiconductor) substrate. The dielectric layer can be any suitabledielectric material and typically has a dielectric constant of about 4or less. For example, the dielectric material can comprise silicondioxide or oxidized silicon dioxides like carbon-doped silicon dioxideand aluminosilicates. The dielectric layer also can be a porous metaloxide, glass, or any other suitable high or low-κ dielectric layer. Thedielectric layer preferably comprises silicon oxide, silicon nitride,silicon oxynitride, silicon carbide, polysilicon, or any othersilicon-containing material with a dielectric constant of about 3.5 orless. The substrate optionally further comprises a secondary layer(e.g., a polishing stop layer). The secondary layer can be a metal layeror a second dielectric layer, and can comprise tungsten, aluminum,tantalum, platinum, rhodium, silicon nitride, silicon carbide, and thelike. In some embodiments, the substrate does not contain any exposedmetal surfaces. According to one preferred embodiment, the substratecomprises a silicon dioxide layer and a silicon nitride layer. Accordingto another preferred embodiment, the substrate comprises only silicondioxide (as in an ILD substrate). According to yet another preferredembodiment, the substrate comprises polysilicon, silicon dioxide, andsilicon nitride. When the substrate comprises a silicon dioxide layerand a silicon nitride layer, typically the silicon dioxide layer ispolished with a selectivity of about 80 or greater relative to thesilicon nitride layer (i.e., the oxide to nitride selectivity is about80 or greater). Preferably, the oxide to nitride selectivity is about100 or greater (e.g., about 120 or greater or even about 150 orgreater).

The CMP system is particularly suited for use in conjunction with achemical-mechanical polishing (CMP) apparatus. Typically, the apparatuscomprises a platen, which, when in use, is in motion and has a velocitythat results from orbital, linear, or circular motion, a polishing padin contact with the platen and moving with the platen when in motion,and a carrier that holds a substrate to be polished by contacting andmoving the substrate relative to the surface of the polishing padintended to contact a substrate to be polished. The polishing of thesubstrate takes place by the substrate being placed in contact with thepolishing pad and then the polishing pad moving relative to thesubstrate, typically with a polishing composition of the inventiontherebetween, so as to abrade at least a portion of the substrate topolish the substrate. The polishing composition can be prepared as asingle slurry that is delivered to the CMP apparatus (e.g., a singleconcentrated slurry that is diluted with water upon delivery), or can beprepared as two slurries containing different chemical components, whichare delivered simultaneously to the polishing pad of the CMP apparatus.

The CMP apparatus can be any suitable CMP apparatus, many of which areknown in the art. The CMP apparatus optionally comprises more than oneplaten such that the substrate can be polished with alternatingpolishing conditions. polishing process can involve periods of alteredpolishing. The CMP apparatus optionally further comprises an endpointdetection system, many of which are known in the art. The polishing padcan be any suitable polishing pad, many of which are known in the art.Desirably, the polishing pad comprises a polishing layer having asurface texture consisting of grooves and/or pores. In some embodimentsit may be desirable to condition the polishing pad. Such polishing padconditioning can be performed in situ or ex situ, for example by adiamond grid. In some embodiments, it may be desirable to periodicallyswitch to delivery of deionized water to the CMP apparatus in place ofthe polishing composition to achieve periodic dilution of the polishingcomposition.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

EXAMPLE 1

This example demonstrates that polishing compositions having a pH ofabout 5 comprising polishing additives having a pK_(a) of about 4 toabout 9 have good silicon dioxide removal rates and high silicon dioxideto silicon nitride selectivity.

Similar substrates comprising silicon dioxide and silicon nitride layerswere polished with different polishing compositions (PolishingCompositions 1A–1W). Each of the polishing compositions comprised 0.5wt. % ceria and sufficient KOH or HNO₃ to adjust the pH to 5. PolishingComposition 1A (control) contained no polishing additive. PolishingCompositions 1B-1O (invention) contained 0.1 wt. % 3-aminophenol,anthranilic acid, piperazine, pyridine, imidazole, pyrrole-2-carboxylicacid, 2,3-pyridinedicarboxylic acid, 3-hydroxypicolinic acid,2-pyridinecarboxylic acid, 4-hydroxybenzoic acid, cyclohexane carboxylicacid, 2-phenylacetic acid, benzoic acid, and glutamic acid,respectively. Polishing Compositions 1P-1W (comparative) contained 0.1wt. % glycine, proline, and benzene sulfonic acid, malic acid, citricacid, oxalic acid, terephthalic acid, salicylic acid, respectively.

The pK_(a) of the functional group of the polishing additive, silicondioxide removal rate (RR), silicon nitride removal rate (RR), andsilicon dioxide to silicon nitride selectivity are summarized in Table1.

TABLE 1 Polishing SiO₂ RR Si₃N₄ RR Composition Polishing Additive pK_(a)(Å/min) (Å/min) Selectivity 1A none — 1810 641 2.8 1B 3-aminophenol 4.3,10 979 55 18 1C anthranilic acid 2.1, 5 320 6 51 1D piperazine 5.3, 9.7873 22 40 1E pyridine 5.2 1742 45 39 1F imidazole 7 874 7 125 1Gpyrrole-2-carboxylic 4.5 511 12 44 acid 1H 2,3-pyridine 3.1, 5.1 225 2111 dicarboxylic acid 1I 3-hydroxy-2-pyridine 1.1, 5.2 826 10 83carboxylic acid 1J 2-pyridine carboxylic 1, 5.4 4794 24 200 acid 1K4-hydroxybenzoic 4.5, 9.3 3705 29 127 acid 1L cyclohexane 4.9 254 6 43carboxylic acid 1M 2-phenylacetic acid 4.3 294 8 36 1N benzoic acid 4.2253 11 24 1O glutamic acid 2.2, 4.4, 10 5025 19 266 1P glycine 2.4, 9.82704 822 3 1Q proline 2, 10.6 2513 824 3 1R benzene sulfonic acid 0.71532 560 3 1S malic acid 3.5, 5.1 103 98 1.1 1T citric acid 3.1, 4.8 92157 0.6 1U oxalic acid 1.3, 4.3 121 406 0.3 1V terephthalic acid 3.5,4.8 598 508 1.2 1W salicylic acid 3, 13.7 734 493 1.5

The data summarized in Table 1 illustrates that polishing additiveshaving a pK_(a) of about 4 to about 9 in a polishing composition canhave a dramatic effect on the oxide and nitride removal rates, as wellas the oxide to nitride selectivity at a pH of about 7 or less.

EXAMPLE 2

This example demonstrates the dependence of substrate layer removalrates and selectivity on the dosage of the polishing additive in thepolishing composition.

Similar substrates comprising silicon dioxide and silicon nitride layerswere polished with different polishing compositions (PolishingCompositions 2A–2C). Each of the polishing compositions comprised 0.3wt. % ceria, a polishing additive at concentrations of 500 ppm, 1000ppm, and 3000 ppm, and sufficient KOH or HNO₃ to adjust the pH to 5.3.Polishing Compositions 2A–2C (invention) contained anthranilic acid,pyrrole-2-carboxylic acid, and 3-hydroxy-2-pyridine carboxylic acid,respectively.

The silicon dioxide removal rate (RR), nitride nitride removal rate(RR), and silicon dioxide to silicon nitride selectivity were determinedfor each of the polishing compositions, and the results are summarizedin Table 2.

TABLE 2 Polishing Polishing Additive SiO₂ RR (Å/min) Si₃N₄ RR (Å/min)Selectivity Composition ppm 500 1000 3000 500 1000 3000 500 1000 3000 2Aanthranilic acid 1842 895 610 <10 <10 <10 184 89 61 2B pyrrole-2- 1380881 760 342 <10 <10 4 88 76 carboxylic acid 2C 3-hydroxy 845 485 120 <10<10 <10 85 48 12 pyridinecarboxylic acid

The data summarized in Table 2 illustrates that the oxide and nitrideremoval rates, as well as the oxide to nitride selectivity, areoptimized at a polishing additive concentration of about 1000 ppm andthat increasing the concentration of polishing additive can actuallydecrease the polishing selectivity.

EXAMPLE 3

This example demonstrates the dependence of the silicon-based dielectriclayer removal rates and selectivity on the pH of the polishingcomposition.

Similar substrates comprising silicon dioxide and silicon nitride layerswere polished with different polishing compositions (PolishingCompositions 3A–3C). Each of the polishing compositions comprised 0.3wt. % ceria and sufficient KOH or HNO₃ to adjust the pH to 4.4, 5.0, or5.6 as indicated. Polishing Compositions 3A–3C (invention) alsocontained 0.1 wt. % anthranilic acid, pyrrole-2-carboxylic acid, and3-hydroxypicolinic acid, respectively.

The silicon dioxide removal rate (RR), silicon nitride removal rate(RR), and selectivity were determined for each of the polishingcompositions, and the results are summarized in Table 3.

TABLE 3 Polishing Polishing Additive SiO₂ RR (Å/min) Si₃N₄ RR (Å/min)Selectivity Composition pH 4.4 5.0 5.6 4.4 5.0 5.6 4.4 5.0 5.6 3Aanthranilic acid 170 895 1023 38 <10 282 4.47 89 3.63 3B pyrrole-2- 95881 1007 <10 <10 149 9.5 88 6.76 carboxylic acid 3C 3-hydroxy-2- 270 485599 <10 <10 19 27 48 31.5 pyridine carboxylic acid

The results summarized in Table 3 demonstrate that the substrate removalrates and selectivity vary as a function of the pH of the polishingcomposition, with a pH of about 5 being preferred.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A method of polishing a substrate comprising: (i) contacting asubstrate comprising a silicon-containing dielectric layer with achemical-mechanical polishing system comprising: (a) about 0.5 wt. % orless of an inorganic abrasive consisting, essentially of ceria, (b) apolishing additive bearing a functional group with a pK_(a) of about 4to about 9, wherein the polishing additive is selected from the groupconsisting of arylamines, aminoalcohols, aliphatic amines, heterocyclicamines, hydroxamic acids, aminocarboxylic acids, cyclic monocarboxylicacids, unsaturated monocarboxylic acids, substituted phenols,sulfonamides, thiols, salts thereof, and combinations thereof, and (c) aliquid carrier, wherein the polishing system has a pH of about 7 or lessand does not contain a significant amount of cross-linked polymerabrasive particles that are electrostatically associated with theinorganic abrasive, and (ii) abrading at least a portion of thesilicon-containing dielectric layer to polish the substrate.
 2. Themethod of claim 1, wherein the functional group is selected from amines,carboxylic acids, alcohols, thiols, sulfonamides, imides, hydroxamicacids, hydrazines, barbituric acids, and combinations thereof.
 3. Themethod of claim 1, wherein the substrate comprises a silicon dioxidelayer and a silicon nitride layer.
 4. The method of claim 1, wherein thepolishing system has a pH of about 2 to about 6.5.
 5. The method ofclaim 4, wherein the polishing system has a pH of about 3.5 to about5.5.
 6. The method of claim 1, wherein the polishing additive is anarylamine compound.
 7. The method of claim 6, wherein the arylaminecompound further comprises one or more substituents selected fromcarboxylic acids, sulfonic acids, phosphonic acids, hydroxyl groups,thiol groups, sulfonamides, salts thereof, and combinations thereof. 8.The method of claim 7, wherein the arylamine compound is selected fromthe group consisting of aniline, anthranilic acid, aminophenols,orthanilic acid, salts thereof, and combinations thereof.
 9. The methodof claim 1, wherein the polishing additive is a heterocyclic aminecompound.
 10. The method of claim 9, wherein the heterocyclic aminecompound is selected from the group consisting of imidazole, quinoline,pyridine, 2-methylpyridine, 2-pyridinecarboxylic acid,pyridinedicarboxylic acids, 2-quinolinecarboxylic acid, morpholine,piperazine, triazoles, pyrrole, pyrrole-2-carboxylic acid, tetrazoles,salts thereof, and combinations thereof.
 11. The method of claim 1,wherein the polishing additive is an aminocarboxylic acid compound. 12.The method of claim 11, wherein the aminocarboxylic acid compound isselected from the group consisting of glutamic acid, aspartic acid,cysteine, histidine, salts thereof, and combinations thereof.
 13. Themethod of claim 1, wherein the polishing additive is a cyclicmono-carboxylic acid compound comprising a C₄₋₁₂ cyclic alkyl or C₆₋₁₂aryl group.
 14. The method of claim 13, wherein the cyclicmonocarboxylic acid is selected from the group consisting of benzoicacid, cyclohexane carboxylic acid, cyclohexylacetic acid, 2-phenylaceticacid, salts thereof, and combinations thereof.
 15. The method of claim1, wherein the polishing additive is selected from the group consistingof unsaturated monocarboxylic acids, hydroxamic acids, and combinationsthereof.
 16. The method of claim 1, wherein the polishing additive isselected from substituted phenols, thiols, sulfonamides, or combinationsthereof.
 17. The method of claim 1, wherein the inorganic abrasive has apositive zeta potential.
 18. The method of claim 1, wherein thepolishing composition has a conductivity of about 2000 μS/cm or less.19. The method of claim 1, wherein the inorganic abrasive is fixed ontoa polishing surface of a polishing pad.
 20. The method of claim 1,wherein the polishing system is colloidally stable over a period of atleast 24 hours.
 21. The method of claim 1, wherein the polishing systemfurther comprises a surfactant.
 22. The method of claim 1, wherein thepolishing system comprises about 0.05 wt. % to about 0.5 wt. % ceriaabrasive.
 23. The method of claim 22, wherein the polishing systemcomprises about 0.1 wt. % to about 0.5 wt. % ceria abrasive.
 24. Themethod of claim 1, wherein the polishing system comprises an inorganicabrasive that consists of ceria abrasive.
 25. The method of claim 1,wherein the ceria abrasive has an average primary particle size of fromabout 50 nm to about 150 nm and an average agglomerate particle size ofabout 300 nm or less, wherein the liquid carrier comprises water, andwherein the ceria is suspended in the water.
 26. A method of shallowtrench isolation processing comprising: (i) providing achemical-mechanical polishing system comprising: (a) about 0.5 wt. % orless of an inorganic abrasive consisting essentially of ceria having anaverage particle size of about 180 nm or less and a positive zetapotential, (b) a polishing additive bearing a functional group with apK_(a) of about 4 to about 9, wherein the polishing additive is selectedfrom the group consisting of arylamines, aminoalcohols, aliphaticamines, heterocyclic amines, hydroxamic acids, aminocarboxylic acids,cyclic monocarboxylic acids, unsaturated monocarboxylic acids,substituted phenols, sulfonamides. thiols, salts thereof, andcombinations thereof, and (c) a liquid carrier, wherein thechemical-mechanical polishing system has a pH of about 4 to about 6,(ii) contacting a shallow trench isolation substrate comprising asilicon dioxide layer and a silicon nitride layer with thechemical-mechanical polishing system, and (iii) abrading at least aportion of the substrate to polish the substrate.
 27. A method ofpolishing an interlayer dielectric device or premetal dielectric devicecomprising (i) providing the chemical-mechanical polishing systemcomprising: (a) about 0.5 wt. % or less of an inorganic abrasiveconsisting essentially of ceria having an average particle size of about180 nm or less and a positive zeta potential, (b) a polishing additivebearing a functional group with a pK_(a) of about 4 to about 9, whereinthe polishing additive is selected from the group consisting ofarylamines, aminoalcohols, aliphatic amines, heterocyclic amines,hydroxamic acids, aminocarboxylic acids, cyclic monocarboxylic acids,unsaturated monocarboxylic acids, substituted phenols, sulfonamides,thiols, salts thereof, and combinations thereof, and (c) a liquidcarrier, wherein the chemical-mechanical polishing system has a pH ofabout 4 to about 6, (ii) contacting a interlayer dielectric layer withthe chemical-mechanical polishing system, and (iii) abrading at least aportion of the interlayer dielectric device to polishing the interlayerdielectric premetal dielectric device.
 28. A method of polishing asubstrate comprising: (i) contacting a substrate comprising a silicondioxide layer and silicon nitride layer with a chemical-mechanicalpolishing system comprising: (a) water, (b) about 0.05 wt. % to about0.5 wt. % inorganic abrasive suspended in the water, wherein theinorganic abrasive consists essentially of ceria having a positive zetapotential, an average primary particle size of from about 50 nm to about150 nm and an average agglomerate particle size of about 300 nm or less,and (c) a polishing additive bearing a functional group with a pK_(a) ofabout 4 to about 9 selected from the group consisting of2-pyridinecarboxylic acid, pyridinedicarboxylic acids,2-quinolinecarboxylic acid, pyrrole-2-carboxylic acid, salts thereof,and combinations thereof, wherein the polishing system has a pH of about3.5 to about 5.5, and (ii) abrading at least a portion of the substrateto polish the substrate.